Instant Pot Bangers and Mash with Onion Gravy - Yay! For Food

Ingredients

• 2 lb. Russet potatoes (2-4), peeled and cut into 1-2 inch cubes
• 4 pork sausages (400 g), preferably British Bangers* (see first note)
• 1 cup water
• Cooked Russet potatoes (see above)
• ½ cup (1 oz) green onions, sliced
• ¼ cup (2 oz) unsalted butter
• 2-4 tbsp milk
• Salt and pepper, to taste
• 1/4 cup (2 oz) unsalted butter, divided
• 1 red onion (10 oz), thinly sliced
• 1 cup + 2 tbsp beef broth, divided
• 2 tbsp balsamic vinegar
• ½ cup water
• 1 tbsp cornstarch